1929 Grand Banks earthquake


The 1929 Grand Banks earthquake occurred on November 18. The shock had a moment magnitude of 7.2 and a maximum Rossi–Forel intensity of VI and was centered in the Atlantic Ocean off the south coast of Newfoundland in the Laurentian Slope Seismic Zone.

Earthquake

The earthquake was centred on the edge of the Grand Banks of Newfoundland, about south of the island. It was felt as far away as New York City and Montreal. The quake, along two faults south of the Burin Peninsula, triggered a large submarine landslide displacing. It snapped 12 submarine transatlantic telegraph cables and led to a tsunami that arrived in three waves. Newfoundland, Canada and Saint Pierre and Miquelon had the largest impact, both from the snapped 12 submarine cables, and the tsunami. This was Canada's largest submarine landslide ever recorded, up to 500 times the size of 1894 Saint-Alban subaerial slide.
In 2002 Natural Resources Canada and the United States Geological Survey, created an intensity map by using the Revised Modified Mercalli scale.

Tsunami

The tsunami waves had an amplitude of, and a runup of along the Burin Peninsula. It destroyed many south coastal communities on the Peninsula, killing 27 or 28 people and leaving 1,000 or more homeless. All means of communication were cut off by the destruction, and relief efforts were further hampered by a blizzard that struck the day after. It was recorded as far away as Lagos, Portugal away, 06:47 after the earthquake. It took 2 hours and 23 minutes to strike Burin, Newfoundland, from the epicenter, and only two hours to be observed in Bermuda.

Prince Edward Island

Prince Edward Island had felt the earthquake; the intensity was rated at the time at IV – VI on the Rossi-Forel scale. In PEI it ranged from an intensity of III – V.

Saint Pierre and Miquelon

In the then named French Republic Overseas territory of Saint Pierre and Miquelon, about west of the Burin Peninsula, people were awakened around 16:30h by the earthquake that lasted approximately one minute. At 17:20, the tsunami reached the island of Saint-Pierre, submerging the docks. The worst damage was reported on the island then named Île-aux-Chiens, now known as L'Île-aux-Marins. The tsunami hit from the south, rising above the height of the south bank that protects the south coast, flooding the lower part of the island. It damaged and moved some of the houses; there were no reported injuries or casualties from the islands. The quake's intensity on the island was V – VI, and on the revised Modified Mercalli Intensity scale IV – V

Aftermath

It took more than three days before the SS Meigle responded to an SOS signal with doctors, nurses, blankets, and food. Donations from across Newfoundland, Canada, the United States and United Kingdom totaled $250,000. There was never an accurate official list of the victims produced by any branch of the Newfoundland government. In the report entitled "Loss of Life," the Honourable Dr. Harris Munden Mosdell, Chairman of the Board of Health Burin West, reported: "The loss of life through the tidal wave totals twenty-seven. Twenty-five deaths were due directly to the upheaval. Two other deaths occurred subsequently and were due to shock and exposure." Later research attributed an additional death to the earthquake.
In 1952, American scientists from Columbia University put together the pieces of the sequentially broken cables that led to the discovery of the landslide and the first documentation of a turbidity current. Scientists have examined other layers of sand believed to be deposited by other tsunamis in an effort to determine the occurrence rates of large earthquakes. One sand layer, thought to be deposited by the 1929 tsunami, at Taylor's Bay was found below the turf line. The occurrences of large tsunamis, such as the one in 1929, are dependent upon deposition of sediments offshore because it was the landslide that made the tsunami so powerful. The deposition of such a large volume of sediments will take a while before there is enough to form an underwater landslide the same size as that in 1929.

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